1. Field of the Invention
The present invention relates to an imaging lens system, and more particularly, to a compact imaging lens system used in imaging or three-dimensional (3D) imaging application of electronic products.
2. Description of the Prior Art
In recent years, with the popularity of portable electronic products having photographing function, the demand of compact imaging lens system has grown. Generally, the sensor of a general photographing camera is none other than CCD (Charge Coupled Device) or CMOS device (Complementary Metal Oxide Semiconductor device). Furthermore, advances in semiconductor manufacturing technology have allowed the pixel size of sensors to be reduced and therefore lead compact imaging lens systems to higher resolution. In the meantime, the demand for better image quality is also increased.
A conventional imaging lens system with high resolving power, such as the one set forth in U.S. Pat. No. 7,365,920, generally has a front stop and four lens elements; wherein, the first and second lens elements are adhered together to form a doublet for correcting the chromatic aberration. However, this kind of arrangement has the following disadvantages. First, the degree of freedom in arranging the lens system is curtailed due to the employment of excessive number of spherical glass lenses; thus, the total track length of the system cannot be reduced easily. Second, the process of adhering glass lenses together is complicated, posing difficulties in manufacturing. Moreover, with the popularity of high level portable electronic products, such as smart phone and PDA (Personal Digital Assistant), the demand for higher pixel-count and image quality of compact imaging lens system increase fast, and the conventional lens system with four lens elements can no longer satisfy the imaging lens systems of even higher level.
In order to satisfy the demand of even higher level, a conventional lens system with five lens elements, such as disclosed in U.S. Pat. No. 7,826,149 or No. 8,072,695, adopts one more lens element to improve the performance of the lens system. However, those conventional lens systems with five lens elements inevitably have the drawback of excessively long total track length, and there are still room for improvement of the resolution of peripheral field and the sensitivity of the image sensor thereof.
Accordingly, the field requires a suitable lens system for compact and portable electronic products, which has good image quality and photosensitivity.